In both biology and the human sciences, social groups are sometimes treated as adaptive units whose organization cannot be reduced to individual interactions. This group-level view is opposed by a more individualistic one that treats social organization as a byproduct of self-interest. According to biologists, group-level adaptations can evolve only by a process of natural selection at the group level. Most biologists rejected group selection as an important evolutionary force during the 1960s and 1970s but a positive literature began to (...) grow during the 1970s and is rapidly expanding today. We review this recent literature and its implications for human evolutionary biology. We show that the rejection of group selection was based on a misplaced emphasis on genes as “replicators” which is in fact irrelevant to the question of whether groups can be like individuals in their functional organization. The fundamental question is whether social groups and other higher-level entities can be “vehicles” of selection. When this elementary fact is recognized, group selection emerges as an important force in nature and what seem to be competing theories, such as kin selection and reciprocity, reappear as special cases of group selection. The result is a unified theory of natural selection that operates on a nested hierarchy of units.The vehicle-based theory makes it clear that group selection is an important force to consider in human evolution. Humans can facultatively span the full range from self-interested individuals to “organs” of group-level “organisms.” Human behavior not only reflects the balance between levels of selection but it can also alter the balance through the construction of social structures that have the effect of reducing fitness differences within groups, concentrating natural selection (and functional organization) at the group level. These social structures and the cognitive abilities that produce them allow group selection to be important even among large groups of unrelated individuals. (shrink)

The definition of biological individuality is one of the most discussed topics in philosophy of biology, but current debate has focused almost exclusively on evolution-based accounts. Moreover, several participants in this debate consider the notions of a biological individual and an organism as equivalent. In this paper, I show that the debates would be considerably enriched and clarified if philosophers took into account two elements. First, physiological fields are crucial for the understanding of biological individuality. Second, the category of biological (...) individuals should be divided into two subcategories: physiological individuals and evolutionary individuals, which suggests that the notions of organism and biological individual should not be used interchangeably. I suggest that the combination of an evolutionary and a physiological perspective will enable biologists and philosophers to supply an account of biological individuality that will be both more comprehensive and more in accordance with scientific practices. (shrink)

In an incendiary 2010 Nature article, M. A. Nowak, C. E. Tarnita, and E. O. Wilson present a savage critique of the best-known and most widely used framework for the study of social evolution, W. D. Hamilton’s theory of kin selection. More than a hundred biologists have since rallied to the theory’s defence, but Nowak et al. maintain that their arguments ‘stand unrefuted’. Here I consider the most contentious claim Nowak et al. defend: that Hamilton’s rule, the core explanatory principle (...) of kin selection theory, ‘almost never holds’. I first distinguish two versions of Hamilton’s rule in contemporary theory: a special version (HRS) that requires restrictive assumptions, and a general version (HRG) that does not. I then show that Nowak et al. are most charitably construed as arguing that HRS almost never holds, while HRG buys its generality at the expense of explanatory power. While their arguments against HRS are fairly uncontroversial, their arguments against HRG are more contentious, yet these have been largely overlooked in the ensuing furore. I consider the arguments for and against the explanatory value of HRG, with a view to assessing what exactly is at stake in the debate. I suggest that the debate hinges on issues concerning the causal interpretability of regression coefficients, and concerning the explanatory function Hamilton’s rule is intended to serve. (shrink)

The ontological dependence of one domain on another is compatible with the explanatory autonomy of the less basic domain. That autonomy results from the fact that the relationship between two domains can be very complex. In this paper I distinguish two different types of complexity, two ways the relationship between domains can fail to be transparent, both of which are relevant to evolutionary biology. Sometimes high level explanations preserve a certain type of causal or counterfactual information which would be lost (...) at the lower level; I argue that this is central to the proper understanding of the adaptationist program. Sometimes high level kinds are multiply realised by lower level kinds: I argue that this is central to the understanding of macroevolution. (shrink)

Many of the most important properties of human groups – including properties that may give one group an evolutionary advantage over another – are properly defined only at the level of group organization. Yet at present, most work on the evolution of culture has focused solely on the transmission of individual-level traits. I propose a conceptual extension of the theory of cultural evolution, particularly related to the evolutionary competition between cultural groups. The key concept in this extension is the emergent (...) group-level trait. This type of trait is characterized by the structured organization of differentiated individuals and constitutes a unit of selection that is qualitatively different from selection on groups as defined by traditional multilevel selection theory. As a corollary, I argue that the traditional focus on cooperation as the defining feature of human societies has missed an essential feature of cooperative groups. Traditional models of cooperation assume that interacting with one cooperator is equivalent to interacting with any other. However, human groups involve differential roles, meaning that receiving aid from one individual is often preferred to receiving aid from another. In this target article, I discuss the emergence and evolution of group-level traits and the implications for the theory of cultural evolution, including ramifications for the evolution of human cooperation, technology, and cultural institutions, and for the equivalency of multilevel selection and inclusive fitness approaches. (shrink)

We develop an account of laboratory models, which have been central to the group selection controversy. We compare arguments for group selection in nature with Darwin's arguments for natural selection to argue that laboratory models provide important grounds for causal claims about selection. Biologists get information about causes and cause-effect relationships in the laboratory because of the special role their own causal agency plays there. They can also get information about patterns of effects and antecedent conditions in nature. But to (...) argue that some cause is actually responsible in nature, they require an inference from knowledge of causes in the laboratory context and of effects in the natural context. This process, cause detection, forms the core of an analogical argument for group selection. We discuss the differing roles of mathematical and laboratory models in constructing selective explanations at the group level and apply our discussion to the units of selection controversy to distinguish between the related problems of cause determination and evaluation of evidence. Because laboratory models are at the intersection of the two problems, their study is crucial for framing a coherent theory of explanation for evolutionary biology. (shrink)

The theory of evolution by natural selection is, perhaps, the crowning intellectual achievement of the biological sciences. There is, however, considerable debate about which entity or entities are selected and what it is that fits them for that role. This article aims to clarify what is at issue in these debates by identifying four distinct, though often confused, concerns and then identifying how the debates on what constitute the units of selection depend to a significant degree on which of these (...) four questions a thinker regards as central. (shrink)

Kin selection and multilevel selection are alternative approaches for studying the evolution of social behaviour, the relation between which has long been a source of controversy. Many recent theorists regard the two approaches as ultimately equivalent, on the grounds that gene frequency change can be correctly expressed using either. However, this shows only that the two are formally equivalent, not that they offer equally good causal representations of the evolutionary process. This article articulates the notion of an ‘adequate causal representation’ (...) using causal graphs, and then seeks to identify circumstances under which kin and multilevel selection do and do not satisfy the test of causal adequacy. 1 Introduction2 The KS and MLS Approaches2.1 The MLS decomposition2.2 The KS decomposition3 Equivalence and Causality4 Two Problem Cases4.1 The non-social trait case4.2 Genotypic selection with meiotic drive5 Casual Adequacy: A Graphical Approach5.1 The basic idea5.2 Graphs with individual and group variables5.3 Cases where KS is causally adequate5.4 Cases where MLS is causally adequate6 Discussion6.1 Relation to previous work. (shrink)

Microbes are generally thought of as unicellular organisms, but we know that many microbes live as parts of biofilms—complex, surface-attached microbial communities numbering millions of cells. Some authors have recently argued in favour of reconceiving biofilms as biological entities in their own right. In particular, some have claimed that multispecies biofilms are evolutionary individuals : 10126–10132 2015). Against this view, I defend the conservative consensus that selection acts primarily upon microbial cells.

Cancer is often seen as a case of multilevel selection, in which selfish cancer cells pursue short-term proliferation to the detriment of the collective. Thus cancer cells are described as ‘cheats’, and an analogy is often drawn between the mechanisms by which organisms fight cancer and the mechanisms by which social groups enforce cooperation. Recently, Andy Gardner and Max Shpak and Jie Lu have argued that cancer is not a true case of multilevel selection, that cancer cells should be not (...) regarded as cheats, and that the analogy between anti-cancer adaptations and suppression mechanisms in social groups is misleading. Their arguments are powerful. However, by drawing on the (presumed) link between cancer and the evolution of multicellularity, the notion that cancer represents a form of selective conflict between cells and organisms can be salvaged. (shrink)

A number of recent biologists have used multi-level selection theory to help explain the major transitions in evolution. I argue that in doing so, they have shifted from a ‘synchronic’ to a ‘diachronic’ formulation of the levels of selection question. The implications of this shift in perspective are explored, in relation to an ambiguity in the meaning of multi-level selection. Though the ambiguity is well-known, it has never before been discussed in the context of the major transitions.

Once upon a time in evolutionary theory, everything happened for the best. Predators killed only the old or the sick. Pecking orders and other dominance hierarchies minimized wasteful conflict within the group. Male displays ensured that only the best and the fittest had mates. In the culmination of this tradition, Wynne-Edwards argued that many species have mechanisms that ensure groups do not over-exploit their resource base. The “central function” of territoriality in birds and other higher animals is “of limiting the (...) numbers of occupants per unit area of habitat”. Species with dominance hierarchies, species with lekking breeding systems, and species with communal breeding regulate their populations. These social mechanisms have population regulation as their “underlying primary function”. Wynne-Edwards argued that these mechanisms evolve through group selection. Populations without such mechanisms are apt to go extinct by eroding their own resource base. (shrink)

One of the major developments in cancer research in recent years has been the construction of models that treat cancer as a cellular population subject to natural selection. We expand on this idea, drawing upon multilevel selection theory. Cancer is best understood in our view from a multilevel perspective, as both a by-product of selection at other levels of organization, and as subject to selection at several levels of organization. Cancer is a by-product in two senses. First, cancer cells co-opt (...) signaling pathways that are otherwise adaptive at the organismic level. Second, cancer is also a by-product of features distinctive to the metazoan lineage: cellular plasticity and modularity. Applying the multilevel perspective in this way permits one to explain transitions in complexity and individuality in cancer progression. Our argument is a reply to Germain’s scepticism towards the explanatory relevance of natural selection for cancer. The extent to which cancer fulfills the conditions for being a paradigmatic Darwinian population depends on the scale of analysis, and the details of the purported selective scenario. Taking a multilevel perspective clarifies some of the complexities surrounding how to best understand the relevance of evolutionary thinking in cancer progression. (shrink)

The fitness of any evolutionary unit can be understood in terms of its two basic components: fecundity (reproduction) and viability (survival). Trade-offs between these fitness components drive the evolution of life-history traits in extant multicellular organisms. We argue that these trade-offs gain special significance during the transition from unicellular to multicellular life. In particular, the evolution of germ–soma specialization and the emergence of individuality at the cell group (or organism) level are also consequences of trade-offs between the two basic fitness (...) components, or so we argue using a multilevel selection approach. During the origin of multicellularity, we study how the group trade-offs between viability and fecundity are initially determined by the cell level trade-offs, but as the transition proceeds, the fitness trade-offs at the group level depart from those at the cell level. We predict that these trade-offs begin with concave curvature in single-celled organisms but become increasingly convex as group size increases in multicellular organisms. We argue that the increasingly convex curvature of the trade-off function is driven by the cost of reproduction which increases as group size increases. We consider aspects of the biology of the volvocine green algae – which contain both unicellular and multicellular members – to illustrate the principles and conclusions discussed. (shrink)

“The Role of the Individual in Evolution” is a prescient yet neglected 1941 work by the 20th century’s most important paleontologist, George Gaylord Simpson. In a curious intermingling of explanation and critique, Simpson engages questions that would become increasingly fundamental in modern biological theory and philosophy. Did individuality, adaptation, and evolutionary causation reside at more than one level: the cell, the organism, the genetically coherent reproductive group, the social group, or some combination thereof? What was an individual, anyway? In this (...) introduction, we highlight two points in a wider historical context. First, recognizing the political context of Simpson’s writing profoundly deepens our understanding of the development of his science as the Modern Evolutionary Synthesis infused biology. Second, this story illuminates the emergence of debates around what would eventually come to be called multilevel selection theory. The organism-centered concept of biological individuality defended by Simpson is situated in relation to the then-emerging Synthesis, in which he was a renowned player, and also in relation to the views he opposed: the “metaphysical” ideas of paleontologists such as Henry Fairfield Osborn, who claimed that some evolutionary trends derived from potentialities already implanted in the germplasm; and the organicist ideas of Ralph W. Gerard and the Chicago School of ecologists, which he derided as all too congenial to totalitarianism. We find parallels between the ways that Simpson thought then about human individuality under totalitarianism and the way he thought about individuality in evolution; not that any causal relationship linked the two, but that commonalities of hierarchical structure exist between single entities and groups in both instances. We then trace the subsequent development of Simpson’s political and philosophical takes on the role of the individual in evolution through the 1960s and lightly sketch out the later fate of the organicist ideas of the Chicago School. Simpson’s paper, originally published in the Journal of the Washington Academy of Sciences, is available as supplementary material in the online version of this article, as part of the "Classics in Biological Theory" collection. (shrink)

Biological individuals are usually defined by evolutionists through a reference to natural selection. This article looks for a concept of individuality that would hold at the same time for organisms and for communities or ecosystems, the latter being unaffected by natural selection. In the wake of Simon’s notion of “quasi-independence,” I elaborate a concept of “weak individuality” defined by probabilistic connections between sub-entities, read off our knowledge of their interactions. This formal scheme of connections allows one to infer what are (...) the individuals in the domain addressed by the theory of the interactions. The article argues that if ecosystems do not have strong individuality, they still possess a weak individuality, ecological theories providing the values of the variables in the formula for individuality. (shrink)

Clade selection is unpopular with philosophers who otherwise accept multilevel selection theory. Clades cannot reproduce, and reproduction is widely thought necessary for evolution by natural selection, especially of complex adaptations. Using microbial evolutionary processes as heuristics, I argue contrariwise, that (1) clade growth (proliferation of contained species) substitutes for clade reproduction in the evolution of complex adaptation, (2) clade-level properties favoring persistence – species richness, dispersal, divergence, and possibly intraclade cooperation – are not collapsible into species-level traits, (3) such properties (...) can be maintained by selection on clades, and (4) clade selection extends the explanatory power of the theory of evolution. (shrink)

Various results show the ‘formal equivalence’ of kin and group selectionist methodologies, but this does not preclude there being a real and useful distinction between kin and group selection processes. I distinguish individual- and population-centred approaches to drawing such a distinction, and I proceed to develop the latter. On the account I advance, the differences between kin and group selection are differences of degree in the structural properties of populations. A spatial metaphor provides a useful framework for thinking about these (...) differences: kin and group selection may be conceptualized as large, overlapping regions of K - G space. I then consider some implications of the account, defend it from possible objections, and further argue that the structural features characteristic of both kin and group selection may recur at multiple levels of biological organization. (shrink)

Traditional approaches in philosophy of biology focus attention on biological concepts, explanations, and theories, on evidential support and inter-theoretical relations. Newer approaches shift attention from concepts to conceptual practices, from theories to practices of theorizing, and from theoretical reduction to reductive retooling. In this article, I describe the shift from theory-focused to practice-centered philosophy of science and explain how it is leading philosophers to abandon fundamentalist assumptions associated with traditional approaches in philosophy of science and to embrace scientific pluralism. This (...) article comes in three parts, each illustrating the shift from theory-focused to practice-centered epistemology. The first illustration shows how shifting philosophical attention to conceptual practice reveals how molecular biologists succeed in identifying coherent causal strands within systems of bewildering complexity. The second illustration suggests that analyzing how a multiplicity of alternative models function in practice provides an illuminating approach for understanding the nature of theoretical knowledge in evolutionary biology. The third illustration demonstrates how framing reductionism in terms of the reductive retooling of practice offers an informative perspective for understanding why putting DNA at the center of biological research has been incredibly productive throughout much of biology. Each illustration begins by describing how traditional theory-focused philosophical approaches are laden with fundamentalist assumptions and then proceeds to show that shifting attention to practice undermines these assumptions and motivates a philosophy of scientific pluralism. (shrink)

What changes when an evolutionary transition in individuality takes place? Many different answers have been given, in respect of different cases of actual transition, but some have suggested a general answer: that a major transition is a change in the extent to which selection acts at one hierarchical level rather than another. The current paper evaluates some different ways to develop this general answer as a way to characterise the property ‘evolutionary individuality’; and offers a justification of the option taken (...) in Clarke :413–435, 2013)—to define evolutionary individuality in terms of an object’s capacity to undergo selection at its own level. In addition, I suggest a method by which the property can be measured and argue that a problem which is often considered to be fatal to that method—the problem of ‘cross-level by-products’—can be avoided. (shrink)

Formal methods developed for modeling levels of selection problems have recently been applied to the investigation of major evolutionary transitions. We discuss two new tools of this kind. First, the ‘near-variant test’ can be used to compare the causal adequacy of predictively equivalent representations. Second, ‘state-variable gestalt-switching’ can be used to gain a useful dual perspective on evolutionary processes that involve both higher and lower level populations.

The levels of selection debate is generally taken to be a debate about how natural selection can occur at the various levels of biological organization. In this paper, we argue that questions about levels of selection should be analyzed separately from questions about levels of organization. In the deflationary proposal we defend, all that is necessary for multilevel selection is that there are cases in which particles are nested in collectives, and that both the collectives and the particles that compose (...) them each separately undergo natural selection. We argue that adopting this deflationary account helps to disentangle the levels of selection and the levels of organization, and thereby contributes to advancing the levels of selection debate. (shrink)

Evolutionary transitions in individuality (ETIs) are events during which individuals at a given level of organization (particles) interact to form higher-level entities (collectives) which are then recognized as new individuals at that level. ETIs are intimately related to levels of selection, which, following Okasha, can be approached from two different perspectives. One, referred to as ‘synchronic’, asks whether selection occurs at the collective level while the partitioning of particles into collectives is taken for granted. The other, referred to as ‘diachronic’, (...) asks about the origins of the partitioning of particles into collectives. After having presented the two perspectives and a classical formalism used to deal with the levels-of-selection question in the literature, namely the multilevel version of the Price equation, I show that because this formalism treats the levels-of-selection question from a synchronic perspective, it is inadequate to explain ETIs. This is because a fundamental aspect of ETIs is the origin of collectives. From there, I develop a framework for levels of selection compatible with the diachronic perspective. This framework relies on the distinction between what I call, on the one hand, a ‘functional aggregative collective trait’, and on the other hand, a ‘functional non-aggregative collective trait’. After having presented this distinction, I implement it in the Price equation, leading to a new statistical partitioning of this equation which, I argue, represents a causal decomposition more relevant for ETIs. Finally, I exploit this partitioning to explain the critical stages of an ETI. In addition to its explanatory power, a measure of the degree of functional non-aggregativity could be used as a proxy for the degree of individuality of a collective. (shrink)

Yes, fitness is the central concept of evolutionary biology, but it is an elusive concept. Almost everyone who looks at it seriously comes out in a different place.

Okasha claims at the outset of his book "Evolution and the Levels of Selection" that the Price equation lays bare the fundamentals underlying all selection phenomena. However, the thoroughness of his subsequent analysis of multi-level selection theories leads him to abandon his fundamentalist commitments. At critical points he invokes cost benefit analyses that sometimes favors the Price approach and sometimes the contextual approach, sometimes favors MLS1 and sometimes MLS2. And although he doesn’t acknowledge it, even the Price approach breaks down (...) into a family of alternative equations that parse the causes in different ways, none of which is uniquely correct and none of which achieves the ultimate isolation of effects due to what Okasha believes are the fundamental causes. I argue that his book provides good reason to re-conceive our understanding of evolutionary theorizing in terms of a toolbox view and to stop subjecting the analyses of evolutionary concepts to a universalist standard. (shrink)

Two alternative statistical approaches to modelling multi-level selection in nature, both found in the contemporary biological literature, are contrasted. The simple covariance approach partitions the total selection differential on a phenotypic character into within-group and between-group components, and identifies the change due to group selection with the latter. The contextual approach partitions the total selection differential into different components, using multivariate regression analysis. The two approaches have different implications for the question of what constitutes group selection and what does not. (...) I argue that the contextual approach is theoretically preferable. This has important implications for a number of issues in the philosophical debate about the levels of selection. Introduction Group selection and the covariance formulation of selection The contextual approach A modification of the simple covariance approach Consequences: frameshifting and additivity 5.1 Frameshifting 5.2 Additivity Conclusion. (shrink)

The emergence of individuality during the evolutionary transition from single cells to multicellularity poses a range of problems. A key issue is how variation in lower‐level individuals generates a corporate (collective) entity with Darwinian characteristics. Of central importance to this process is the evolution of a means of collective reproduction, however, the evolution of a means of collective reproduction is not a trivial issue, requiring careful consideration of mechanistic details. Calling upon observations from experiments, we draw attention to proto‐life cycles (...) that emerge via unconventional routes and that transition, in single steps, individuality to higher levels. One such life cycle arises from conflicts among levels of selection and invokes cheats as a primitive germ line: it lays the foundation for collective reproduction, the basis of a self‐policing system, the selective environment for the emergence of development, and hints at a plausible origin for a soma/germ line distinction. (shrink)

All disciplines must define their basic units and core processes. In evolutionary biology, the core process is natural selection and the basic unit of selection and adaptation is the individual. To operationalize the theory of natural selection we must count individuals, as they are the bearers of fitness. While canonical individuals have often been taken to be multicellular organisms, the hierarchy of life shows that new kinds of individuals have evolved. A variety of criteria have been used to define biological (...) individuality. Some criteria rely on the presence/absence of a particular property while others advocate an approach that reflects the process of natural selection. The plethora of approaches to classifying individuality has resulted in confusion regarding how to study individuality in a given taxon. (shrink)

The conflation of two fundamentally distinct issues has generated serious confusion in the philosophical and biological literature concerning the units of selection. The question of how a unit of selection of defined, theoretically, is rarely distinguished from the question of how to determine the empirical accuracy of claims--either specific or general--concerning which unit(s) is undergoing selection processes. In this paper, I begin by refining a definition of the unit of selection, first presented in the philosophical literature by William Wimsatt, which (...) is grounded in the structure of natural selection models. I then explore the implications of this structural definition for empirical evaluation of claims about units of selection. I consider criticisms of this view presented by Elliott Sober--criticisms taken by some (for example, Mayo and Gilinsky 1987) to provide definitive damage to the structuralist account. I shall show that Sober has misinterpreted the structuralist views; he knocks down a straw man in order to motivate his own causal account. Furthermore, I shall argue, Sober's causal account is dependent on the structuralist account that he rejects. I conclude by indicating how the refined structural definition can clarify which sorts of empirical evidence could be brought to bear on a controversial case involving units of selection. (shrink)

In models of multi-level selection, the property of Darwinian fitness is attributed to entities at more than one level of the biological hierarchy, e.g. individuals and groups. However, the relation between individual and group fitness is a controversial matter. Theorists disagree about whether group fitness should always, or ever, be defined as total (or average) individual fitness. This paper tries to shed light on the issue by drawing on work in social choice theory, and pursuing an analogy between fitness and (...) utility. Social choice theorists have long been interested in the relation between individual and social utility, and have identified conditions under which social utility equals total (or average) individual utility. These ideas are used to shed light on the biological problem. (shrink)

The contrast between the strategies of research employed in reductionism and holism masks a radical contradiction between two different scientific philosophies. We concentrate in particular on an analysis of the key philosophical issues which give structure to holistic thought. A first (non-exhaustive) analysis of the philosophical tradition will dwell upon: a) the theory of emergence: each level of organisation is characterised by properties whose laws cannot be deduced from the laws of the inferior levels of organisation (Engels, Morgan); b) clarification (...) of the relations between the “whole” and the “parts” (Woodger, Needham); c) the ontological or epistemological nature of the emergent properties; are they a phenomenological reality or solely an artefact of the state of our knowledge? (Pepper, Henle, Hempel and Oppenheim); d) the proposition of the holistic theoretical and methodological model ( Novikoff, Feibleman). I then go on to examine the differences that exist between the reductionist and the holistic approaches at various levels of analysis: that is to say, the differences which affect their ontologies, methodologies and epistemologies respectively. I attempt to understand the spirit of a holistic approach to ecology by analyzing the major work of E.P. Odum Fundamentals of ecology (1953, 1959, 1971). I set forward what might be meant by the “holistic approach”, which is implicated in all the different levels of organisation at which the problem of “complexity” is debated. Ecology presents itself as an “holistic science” and Odum’s book offers a vision of the world which dates far back in the history of philosophy. By looking at the three different editions of this fundamental text on ecology, we may become aware of the evolution of Odum’s thought. In fact, only in the third and last edition is there a conscious appropriation of the holistic approach (by using the theoretical models of Feibleman who, for his part, refers to Novikoff). However, even when formally referring to the theory of emergence (that is to say the ontological nucleus of every holistic approach), Odum’s systemic analysis presents the same logical errors, which push him back into the reductionist domain. Above all, in his examination of the main concepts of “population”, “community” and “ecosystem”, there is a misunderstanding of the profound difference between “collective properties” and “emergent properties”. Moreover, the cybernetic models of Odum’s systemic analysis (introduced into ecology by Margalef), allowed him to vastly oversimplify his methodological task: in fact, neither how many levels nor which levels of organization are fundamental for the study of each individual level is clearly marked. Finally, Odum analyses the ecosystem as composed of energetic flux and cycles of matter, referring to the trophic-dynamic vision of Lindeman. That is to say, in my opinion, he juxtaposes a reductionistic methodology and epistemology to an holistic ontology. (shrink)

Multi-level selection can be understood via the Price equation or contextual analysis, which offer incompatible statistical decompositions of evolutionary change into components of group and individual selection. Okasha argued that each approach suffers from problem cases. I introduce further problem cases for the Price approach, arguing that it is appropriate for MLS 2 group selection but not MLS 1. I also show that the problem cases Okasha raises for contextual analysis can be resolved. For some such cases, however, it emerges (...) that there is no determinate answer to the question of how much of the total selective effect was due to group selection compared to individual selection. This suggests that when there is interaction between the effect of group character and individual character, one cannot separate selection into distinct ‘levels’ at all. (shrink)

In response to Germain argument that evolution by natural selection has a limited explanatory power in cancer, Lean and Plutynski have recently argued that many adaptations in cancer only make sense at the tumor level, and that cancer progression mirrors the major evolutionary transitions. While we agree that selection could potentially act at various levels of organization in cancers, we argue that tumor-level selection is unlikely to actually play a relevant role in our understanding of the somatic evolution of human (...) cancers. (shrink)

In multicellular organisms, cells are frequently programmed to die. This makes good sense: cells that fail to, or are no longer playing important roles are eliminated. From the cell’s perspective, this also makes sense, since somatic cells in multicellular organisms require the cooperation of clonal relatives. In unicellular organisms, however, programmed cell death poses a difficult and unresolved evolutionary problem. The empirical evidence for PCD in diverse microbial taxa has spurred debates about what precisely PCD means in the case of (...) unicellular organisms. In this article, we survey the concepts of PCD in the literature and the selective pressures associated with its evolution. We show that definitions of PCD have been almost entirely mechanistic and fail to separate questions concerning what PCD fundamentally is from questions about the kinds of mechanisms that realize PCD. We conclude that an evolutionary definition is best able to distinguish PCD from closely related phenomena. Specifically, we define “true” PCD as an adaptation for death triggered by abiotic or biotic environmental stresses. True PCD is thus not only an evolutionary product but must also have been a target of selection. Apparent PCD resulting from pleiotropy, genetic drift, or trade-offs is not true PCD. We call this “ersatz PCD.”. (shrink)

Okasha, in Evolution and the Levels of Selection, convincingly argues that two rival statistical decompositions of covariance, namely contextual analysis and the neighbour approach, are better causal decompositions than the hierarchical Price approach. However, he claims that this result cannot be generalized in the special case of soft selection and argues that the Price approach represents in this case a better option. He provides several arguments to substantiate this claim. In this paper, I demonstrate that these arguments are flawed and (...) argue that neither the Price equation nor the contextual and neighbour partitionings sensu Okasha are adequate causal decompositions in cases of soft selection. The Price partitioning is generally unable to detect cross-level by-products and this naturally also applies to soft selection. Both contextual and neighbour partitionings violate the fundamental principle of determinism that the same cause always produces the same effect. I argue that a fourth partitioning widely used in the contemporary social sciences, under the generic term of ‘hierarchical linear model’ and related to contextual analysis understood broadly, addresses the shortcomings of the three other partitionings and thus represents a better causal decomposition. I then defend this model against the argument that because it predicts that there is some organismal selection in some specific cases of segregation distortion then it should be rejected. I show that cases of segregation distortion that intuitively seem to contradict the conclusion drawn from the hierarchical linear model are in fact cases of multilevel selection 2 while the assessment of the different partitionings are restricted to multilevel selection 1. (shrink)

Eusociality is broadly defined as: colonies consisting of overlapping generations, cooperative brood care, and a reproductive division of labour where sterile (or non-reproductive) workers help the reproductive members. Colonies of many complex eusocial insect species (e.g. ants, bees, termites) exhibit traits, at the collective level, that are more analogous to biological individuals rather than to groups. Indeed, due to this, colonies of the most complex species are typically a unit of selection, which has led many authors to once again apply (...) the concept of the superorganism to eusocial insects. However, unlike W. M. Wheeler, who originally employed the concept from a physiological and evolutionary perspective, today the superorganism is typically understood only from an evolutionary perspective, using group selection. This is because of the widely held view that eusocial colonies are self-organized systems. According to this view, even the most complex eusocial systems can be explained by appealing to a set of local interactions between parts of an initially disordered system (i.e. self-organization), without the need of any hierarchical control. In this paper we challenge the presupposition that hierarchical control and regulation is not possible in complex eusocial colonies. Using a case study of honey bees (Apis mellifera), we develop an alternative to the self-organization approach, that focuses on the hierarchical nature of the organization of complex eusocial systems—that we refer to as the hierarchical-organizational approach. In addition, we will analyse how colonies of eusocial insects show a complex set of interactions between the different organisms that bring forth a new cohesive collective organization, and how in turn the constitutive entities of this collective organization are transformed in this process. This paper argues that an inter-identity (namely the superorganism) emerges at the collective level in complex eusocial colonies, such as honey bees, due to the hierarchically-organized network of interactions within the colony. (shrink)

On the basis of distinctions between those properties of entities that can be defined without reference to other entities and those that (in different ways) cannot, this note argues that non-trivial forms of frequency-dependent selection of entities should be interpreted as selection occurring at a level higher than that of those entities. It points out that, except in degenerately simple cases, evolutionary game-theoretic models of selection are not models of individual selection. Similarly, models of genotypic selection such as heterosis cannot (...) be legitimately interpreted as models of genic selection. The analysis presented here supports the views that: (i) selection should be viewed as a multi-level process; (ii) upper-level selection is ubiquitous; (iii) kin selection should be viewed as a type of group selection rather than individual selection; and (iv) inclusive fitness is not an individual property. (shrink)

Two controversies exist regarding the appropriate characterization of hierarchical and adaptive evolution in natural populations. In biology, there is the Wright-Fisher controversy over the relative roles of random genetic drift, natural selection, population structure, and interdemic selection in adaptive evolution begun by Sewall Wright and Ronald Aylmer Fisher. There is also the Units of Selection debate, spanning both the biological and the philosophical literature and including the impassioned group-selection debate. Why do these two discourses exist separately, and interact relatively little? (...) We postulate that the reason for this schism can be found in the differing focus of each controversy, a deep difference itself determined by distinct general styles of scientific research guiding each discourse. That is, the Wright-Fisher debate focuses on adaptive process, and tends to be instructed by the mathematical modeling style, while the focus of the Units of Selection controversy is adaptive product, and is typically guided by the function style. The differences between the two discourses can be usefully tracked by examining their interpretations of two contested strategies for theorizing hierarchical selection: horizontal and vertical averaging. (shrink)

In an illuminating article, Claus Beisbart argues that the recently-popular thesis that the probabilities of statistical mechanics (SM) are Best System chances runs into a serious obstacle: there is no one axiomatization of SM that is robustly best, as judged by the theoretical virtues of simplicity, strength, and fit. Beisbart takes this 'no clear winner' result to imply that the probabilities yielded by the competing axiomatizations simply fail to count as Best System chances. In this reply, we express sympathy for (...) the 'no clear winner' thesis. However, we argue that an importantly different moral should be drawn from this. We contend that the implication for Humean chances is not that there are no SM chances, but rather that SM chances fail to be sharp. (shrink)

This paper surveys recent philosophy of biology. It aims to introduce outsiders to the field to the recent literature (which is reviewed in the footnotes) and the main recent debates. I concentrate on three of these: recent critiques of the replicator/vehicle distinction and its application to the idea of the gene as the unit of section; the recent defences of group selection and the idea that standard alternatives to group selection are in fact no more than a disguised form of (...) group selection; and recent ideas on the role of selection in evolution, especially the role of selection in structuring the large-scale history of life. The paper connects philosophy of biology to some more general problems in the philosophy of science, and concludes with a few suggestions about unfinished business. (shrink)

In this article I explore some statistical difficulties confronting going conceptions of ‘group’ as understood in accounts of group selection. Most such theories require real groups but define the reality of groups in ways that make it impossible to test for their reality. There are alternatives, but they either require or invite a nominalism about groups that many theorists abjure.

This PhD dissertation examines the conceptual and theoretical foundations of the most general and most widely used framework for understanding social evolution, W. D. Hamilton's theory of kin selection. While the core idea is intuitive enough (when organisms share genes, they sometimes have an evolutionary incentive to help one another), its apparent simplicity masks a host of conceptual subtleties, and the theory has proved a perennial source of controversy in evolutionary biology. To move towards a resolution of these controversies, we (...) need a careful and rigorous analysis of the philosophical foundations of the theory. My aim in this work is to provide such an analysis. I begin with an examination of the concepts behavioural ecologists employ to describe and classify types of social behaviour. I stress the need to distinguish concepts that are often conflated: for example, we need to distinguish simple cooperation from collaboration in collective tasks, behaviours from strategies, and control from manipulation and coercion. I proceed from here to the formal representation of kin selection via George R. Price’s covariance selection mathematics. I address a number of interpretative issues the Price formalism raises, including the vexed question of whether kin selection theory is ‘formally equivalent’ to multi-level selection theory. In the second half of the dissertation, I assess the uses and limits of Hamilton’s rule for the evolution of social behaviour; I provide a precise statement of the conditions under which the rival neighbour-modulated fitness and inclusive fitness approaches in contemporary kin selection theory are equivalent (and describe cases in which they are not); and I criticize recent formal attempts to establish the controversial claim that kin selection leads to organisms behaving as if maximizing their inclusive fitness. (shrink)

The species category is defined as thesmallest historical individual within which there is a parental pattern of ancestry and descent. The use of historical individual in this definition is consistent with the prevailing notion that speciesper se are not involved in processes — they are effects, not effectors. Reproductive isolation distinguishes biparental historical species from their parts, and it provides a basis for understanding the nature of the evidence used to discover historical individuals.

The received view in the history of the philosophy of psychology is that the logical positivists—Carnap and Hempel in particular—endorsed the position commonly known as “logical” or “analytical” behaviourism, according to which the relations between psychological statements and the physical-behavioural statements intended to give their meaning are analytic and knowable a priori. This chapter argues that this is sheer legend: most, if not all, such relations were viewed by the logical positivists as synthetic and knowable only a posteriori. It then (...) traces the origins of the legend to the logical positivists’ idiosyncratic extensional or at best weakly intensional use of what are now considered crucially strongly intensional semantic notions, such as “translation,” “meaning” and their cognates, focussing on a particular instance of this latter phenomenon, arguing that a conflation of explicit definition and analyticity may be the chief source of the legend. (shrink)

I investigate the relationship between adaptation, as defined in evolutionary theory through natural selection, and the concept of emergence. I argue that there is an essential correlation between the former, and “emergence” defined in the field of algorithmic simulations. I first show that the computational concept of emergence (in terms of incompressible simulation) can be correlated with a causal criterion of emergence (in terms of the specificity of the explanation of global patterns). On this ground, I argue that emergence in (...) general involves some sort of selective processes. Finally, I show that a second criterion, concerning novel explanatory regularities following the emergence of a pattern, captures the robustness of emergence displayed by some cases of emergence (according to the first criterion). Emergent processes fulfilling both criteria are therefore exemplified in evolutionary biology by some so-called “innovations”, and mostly by the new units of fitness or new kinds of adaptations (like sexual reproduction, multicellular organisms, cells, societies) sometimes called “major transitions in evolution”, that recent research programs (Maynard-Smith and Szathmary 1995 ; Michod 1999 ) aims at explaining. (shrink)

In this contribution, I comment on Raffaella Campaner’s defense of explanatory pluralism in psychiatry (in this volume). In her paper, Campaner focuses primarily on explanatory pluralism in contrast to explanatory reductionism. Furthermore, she distinguishes between pluralists who consider pluralism to be a temporary state on the one hand and pluralists who consider it to be a persisting state on the other hand. I suggest that it would be helpful to distinguish more than those two versions of pluralism – different understandings (...) of explanatory pluralism both within philosophy of science and psychiatry – namely moderate/temporary pluralism, anything goes pluralism, isolationist pluralism, integrative pluralism and interactive pluralism. Next, I discuss the pros and cons of these different understandings of explanatory pluralism. Finally, I raise the question of how to implement or operationalize explanatory pluralism in scientific practice; how to structure the “genuine dialogue” or shape “the pluralistic attitude” Campaner is referring to. As tentative answers, I explore a question-based framework for explanatory pluralism as well as social-epistemological procedures for interaction among competing approaches and explanations. (shrink)

In this paper, I identify two general positions with respect to the relationship between environment and natural selection. These positions consist in claiming that selective claims need and, respectively, need not be relativized to homogenous environments. I then show that adopting one or the other position makes a difference with respect to the way in which the effects of selection are to be measured in certain cases in which the focal population is distributed over heterogeneous environments. Moreover, I show that (...) these two positions lead to two different interpretations—the Pricean and contextualist ones—of a type of selection scenarios in which multiple groups varying in properties affect the change in the metapopulation mean of individual-level traits. Showing that these two interpretations stem from different attitudes towards environmental homogeneity allows me to argue: that, unlike the Pricean interpretation, the contextualist interpretation can only claim that drift or selection is responsible for the change in frequency of the focal trait in a given metapopulation if details about whether or not group formation is random are specified; that the traditional main objection against the Pricean interpretation—consisting in arguing that the latter takes certain side-effects of individual selection to be effects of group selection—is unconvincing. This leads me to suggest that the ongoing debate about which of the two interpretations is preferable should concentrate on different issues than previously thought. (shrink)